The present invention relates to a mechanism for protecting the hard disk assembly of a Winchester type hard disk drive, and, in particular, to a mechanism for lifting the read/write head off of the disk media during a power off condition to protect the head and the media from damage and possible loss of data.
A highly preferred mass data storage device for digital computers is a hard disk drive, and particularly a Winchester type hard disk drive. In this well known technology, data is magnetically recorded onto and read from both sides of a relatively inflexible disk which rotates at a very high speed. The disk generally is comprised of a substrate, such as aluminum, which has been coated with a magnetic sensitive substance such as gamma ferric oxide. Alternatively, the substrate may be plated or splattered by metallic particles, such as cobalt/nickle. As the disk rotates, digital information is recorded onto or read from each of the two planar surfaces of the disk by a pair of small heads, each of which is supported above the surface of the disk by the slipstream of air created by the high rate of rotation of the disk. Therefore, the head "files" on this air bearing just barely above the surface of the disk, for example in the range of 6-20 microinches. Hard disk drives of the Winchester type are preferred over the flexible data storage media, such as floppy disk drives, because of the high data density, reliability and convenience.
The improved density of a hard disk drive is accomplished because of the very low flying height of the head. Although the low flying height increases the risk of "crash", i.e., the unintended contact between the head and the disk media, this risk is reduced because of the sealed environment of the disk drive. That is, the disk drive is impervious to dust or dirt which could cause the head to crash on the disk media. There is no manual handling or operation of the disk drive, further insuring its reliability. Winchester type hard disk drives are fully self-contained and automatically actuated. Thus, in addition to their reliability, they also generally have much longer life than floppy type disk drives which are frequently handled by the user. In addition, the convenience of the hard disk drive is highly advantageous because it can be manufactured as an integral part of the main computer, being incorporated into the CPU frame.
Over the past few years, there has been a rapid trend toward the miniaturization of computers, and in particular personal computers. This trend has led to computers which are small enough to be readily transported by their owners from home to office, etc. Although the portability of such computers increases their utility to the personal computer owner, it also increases the likelihood of damage to the sensitive computer components, and in particular the hard disk drive contained therein.
As the size of computers has decreased, there has also been an increasing demand to reduce the size of the Winchester type hard disk drive. At the same time, there is a need to construct such disk drives so as to be resistant to shock and vibration when not in operation. If the head of the hard disk assembly is permitted to contact or "slap" the surface of the disk, damage to the head and disk media can easily result, with a consequent loss of the data stored on the hard disk. Such slapping can easily result from the shock or vibration which the computer experiences. Furthermore, slapping can cause the magnetic coating of the hard disk drive to chip off, thus increasing the risk of a head crash in future operation.
In order to combat the potential for damage due to shock and vibration, hard disk drive manufacturers have devised shock isolator mountings for the head disk assembly. Lapine Technology, assignee of the present application is the owner of copending application Ser. No. 628,186, filed July 6, 1984, directed to an improved shock mounting, which is incorporated herein by reference.
Other disk drive manufacturers have provided dedicated head landing and take-off zones on the hard disk to avoid the loss of data from head slap. However, such landing zones do not obviate the possibility of damage to the head, nor do they reduce the risk of head crash caused by flaked off bits of the disk coating caused by a previous slap. Furthermore, when the head is permitted to land on the media, it can become stuck there the next time the computer is in use and cause damage to the head. Thus, both the landing and take-off must be very controlled in order to avoid damage to the head. Preferably, the takeoff is very rapid so that the frictional contact between the head and the disk will not cause damage to either one.
In addition, the loading of the head on the disk must also be accomplished in a very controlled fashion. Loading generally refers to the positioning of the head in its flying position above the disk for accomplishing its read/write functions. Loading can either be static or dynamic, referring to the lack of rotation or rotation, respectively, of the disk when loading occurs. For static loading, the head must be loaded very slowly so that a sufficient air bearing is built up under the head in order to permit it to fly above the disk.
Thus, there remains a great need and demand for a mechanism that can keep the head from contact with the disk during a power off situation. Lapine Technology has developed one form of such a head lifter device which is the subject of application Ser. No. 628,689, filed July 6, 1984, which application is hereby incorporated by reference.